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A quick primer on using PHP objects

From: Accessing Databases with Object-Oriented PHP

Video: A quick primer on using PHP objects

If you haven't worked with PHP Objects before, this quick primer will Functions defined by a class are referred to as the object's methods.

A quick primer on using PHP objects

If you haven't worked with PHP Objects before, this quick primer will provide you with sufficient knowledge to follow the instructions in this course. So what are objects? An object is a data type that can store and manipulate values. You create an object from a class, which defines what an object can do. A class is basically a collection of related functions and values packaged as a single unit. We'll be working with PHP built in classes, so there's no need to create the class definitions yourself.

It's all done for you by PHP. Functions defined by a class are referred to as the object's methods. Values stored by an object are referred to as the object's properties. A common example that's used to describe objects is a car, so we'll use that here. An important property of any car is its color. For example you might have a red car, or it could be blue. Other important properties are the make of the car and the number of miles on the clock. All cars share similar properties, but each car is unique.

Similarly, each object that you create from a PHP class is unique. Methods dictate what an object can do. In the case of a car, accelerate is a useful method. Although all cars can accelerate, they operate independently of each other. In programming terms, you create an instance of a class, or instantiate an object. This simply involves using the class's constructor method with the new operator and storing the object in a variable.

The constructor method has the same name as the class, and it often accepts one or more arguments to initialize the object's properties. In our very simple example, we're passing red as the argument to the constructor. And we get a red car. You can create more than one object from the same class. So this creates another car, this time it's blue. You access an object's properties using the arrow operator, which consists of a hyphen and a greater than symbol.

Just append the arrow operators with a variable that contains the object, followed by the name of the property. The arrow operator is also used to call an object's methods. So if car objects have stop and accelerate methods, you can make car2 stop, while car2 accelerates away. So what does this got to do with database objects? Quite simply, the PDO and MySQLi classes that we'll be working with create objects that connect to the database.

The example files use only one connection object, but you could create multiple objects to connect to different databases. Each object is independent, so you could use them to transfer data from one database to another. You use the connection object's methods to interact with the database, such as to execute queries. Methods are basically functions, so they can take arguments. Class constants are frequently used as arguments. Constants are all in uppercase. PDO constants begin with PDO and a double colon, which is known as the scope resolution operator.

MySQLi constants begin with MySQLi underscore. Calling an object's method often returns a new object. This usually contains the results of a query or a prepared statement. For example, if you call the database connection object's query method, and pass it a select query, it returns an object containing the result set in both PDO and MySQLi. Notice that you don't need to use the new operator when an object is returned like this.

The new object will have methods of its own. Just remember to use the arrow operator to call the object's methods. Similarly, use the arrow operator to access an object's properties. And that's really all you need to know about PHP objects to follow the rest of this course.

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This video is part of

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Accessing Databases with Object-Oriented PHP

47 video lessons · 1909 viewers

David Powers
Author

 
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  1. 13m 33s
    1. Welcome
      1m 4s
    2. What you should know before watching this course
      2m 8s
    3. Using the exercise files
      4m 56s
    4. Setting SQLite permissions
      1m 11s
    5. A quick primer on using PHP objects
      4m 14s
  2. 10m 12s
    1. Overview of PHP database APIs
      4m 5s
    2. Using prepared statements
      4m 24s
    3. Using transactions
      1m 43s
  3. 48m 57s
    1. Creating a database source name
      2m 3s
    2. Connecting to a database with PDO
      7m 27s
    3. Looping directly over a SELECT query
      3m 49s
    4. Fetching a result set
      8m 3s
    5. Finding the number of results from a SELECT query
      7m 14s
    6. Checking if a SELECT query contains results
      3m 32s
    7. Executing simple non-SELECT queries
      6m 2s
    8. Getting error messages
      7m 17s
    9. Using the quote() method to sanitize user input
      3m 30s
  4. 39m 51s
    1. Binding input and output values
      2m 36s
    2. Using named parameters
      9m 51s
    3. Using question marks as anonymous placeholders
      2m 35s
    4. Passing an array of values to the execute() method
      5m 20s
    5. Binding results to variables
      7m 53s
    6. Executing a transaction
      6m 54s
    7. Closing the cursor before running another query
      4m 42s
  5. 21m 20s
    1. Generating an array from a pair of columns
      2m 44s
    2. Setting an existing object's properties with a database result
      4m 42s
    3. Creating an instance of a specific class with a database result
      6m 1s
    4. Reusing a result set
      7m 53s
  6. 38m 14s
    1. Connecting to a database with MySQLi
      5m 57s
    2. Setting the character set
      1m 57s
    3. Submitting a SELECT query and getting the number of results
      4m 4s
    4. Fetching the result
      7m 35s
    5. Rewinding the result for reuse
      3m 20s
    6. Handling non-SELECT queries
      5m 27s
    7. Getting error messages
      5m 47s
    8. Sanitizing user input with real_escape_string()
      4m 7s
  7. 27m 49s
    1. Initializing and preparing a statement
      4m 17s
    2. Binding parameters and executing a prepared statement
      5m 55s
    3. Binding output variables
      5m 6s
    4. Executing a MySQLi transaction
      7m 5s
    5. Dealing with "commands out of sync" in prepared statements
      5m 26s
  8. 24m 7s
    1. Buffered and unbuffered queries
      4m 19s
    2. Using real_query()
      6m 1s
    3. Freeing resources that are no longer needed
      2m 31s
    4. Submitting multiple queries
      6m 41s
    5. Creating an instance of a class from a result set
      4m 35s
  9. 3m 31s
    1. PDO and MySQLi compared
      3m 31s

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